... exposure to light. Anything starting with poly- is sensitive to light, and sunlight makes it brittle.
YMMV: I have some fat 1/4" polypropylene rope outside now for some many
(six?) years, and it (a) wasn't new when I salvaged it (beach-combing --
exercise for the curious; and if golf is a sport, so too BC!) and (b) looks
none the worse for the exposure. => black, smushed-oval (vs. round)
monofilaments. In Commercial Fishing cordage I see much PP that looks
pretty good -- black is prevalent, also yellow, and orange for some used
in a kernmantle (my def.) form.
Which, yes, is quite a contrast to bits one can find where (a) much
is missing, embrittled to splintery bits, and (b) what remains is but
a quite
pale imitation of the original -- comically, some former
yellow(2strands)&black(1) laid rope 1/4" sapling guy line with now
just whitish remains of 2 strands and the lone black doing the work!
But, to the point: there seems to be some fairly effective means of
mitigating UV's deteriorating effects on (esp.) PP, and you just have
to get the good stuff! Of what I've seen of the CoEx PP/PE cordage,
it resists (allegedly better than PP -- of PP of SOME quality) UV, and
in demise isn't stiff so much as powdery, having been flat-fibered.
-- small consolation re use & strength, but at least less a pain in
the hands (but maybe less readily observed & retired!).
(Recall I posted here a photo of some most peculiar yellow PP of
a ladder hoist line: ONE strand was well embrittled & splintering;
the other two very little so!? -- that's mystery to me.)
- - - - - - -
Re the tying & structure, I'd think that you might need a support in
the center of your 30' span. The loser end posts could work to some
advantage if set with some incline towards center span, anticipating
then subsequent adjustment tightening at the anchor-post spans
which will tend to bring them more upright.
Yes, some variation of a Trucker's Hitch can work. Beware that what
you get in this with cordage sheaves (as opposed to some bits of
metal for less friction, or --best-- a pulley) is more good hold of the
tightening your surge of effort hauling puts in than actual mechanical
advantage -- which you DO get some of, but well less than what is
theoretically there. (The Truckers is theoretically 3:1, but actually
more like 1.5:1.)
And you seen the point of the aforementioned "incline to center":
tightening this from the ends will bring the posts along with the
rope (friction) and so not need to overcome that friction to pass
rope to the hauling end (so much). -- otherwise, one will have
to overcome the friction over the tops of the posts (if one is
running the line merely over the top).
--dl*
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